The invention relates to friction clutches in general and, more particularly, to improvements in friction clutches which can be utilized in motor vehicles in the power trains between the prime movers and the wheels of such vehicles. Still more particularly, the invention relates to improvements in friction clutches of the type wherein a pressure plate is movable axially of and is rotatable with a housing which receives torque from a prime mover (e.g., a flywheel which is driven by the camshaft, crankshaft or another rotary output element of a combustion engine) and wherein a diaphragm spring is installed between the housing and the pressure plate to bias the latter against a clutch plate or clutch disc which is to transmit torque to a driven part, e.g., the input shaft of a variable-speed transmission, in the engaged condition of the clutch.
Friction clutches of the above-outlined character can further comprise a composite seat for an intermediate portion of the diaphragm spring. A radially outer portion of such spring bears against the pressure plate in the engaged condition of the clutch and a radially inner portion (particularly an inner portion including the free ends or tips of resilient prongs forming part of the spring and extending radially inwardly from the radially outer portion) can be moved axially of the housing (e.g., by a bearing or the like) to disengage the clutch. If the clutch is a so-called push-type clutch, the radially inner portion of the diaphragm spring must be depressed axially of the housing in a direction toward the pressure plate in order to disengage the clutch. The intermediate portion of the spring is tiltable relative to two coaxial seats of the composite seat including a first seat between a bottom wall or end wall of the housing and a second seat at that side of the intermediate portion of the spring which faces away from the bottom wall of the housing.
Friction clutches of the above outlined character are disclosed, for example, in published German patent applications Nos. 34 20 109 and 34 40 827, and in published British patent application No. 2 102 899. Reference may also be had to commonly owned U.S. Pat. No. 4,989,710 granted Feb. 5, 1991 to Reik et al. This patent shows a prime mover which drives the housing and a transmission receiving torque from the clutch plate or disc of the patented friction clutch. The disclosure of this patent is incorporated herein by reference.